The successful placement of endosseous dental implants has been well documented for over 30 years; however, the success of these endosseous dental implants has been limited by the quality and quantity of existing bone a given patient would present with. Due to the destructive nature of dentures to the underlying jaw bone as well as to the fact that bone that is not internally stimulated by tooth roots will atrophy, the amount of bone in many people is very limited for the placement of dental implants, especially for those who have been missing teeth for an extended period of time.
Bone grafting has become an essential element for the successful treatment of those who do not have enough bone for dental implants. As viable methods, blocks of hip bone have been affixed to the jaw, and freeze-dried demineralized bone protein has been used as a stimulant to cause the patient's bone cells to become active and lay down new bone onto the existing bone areas and into the new bone graft areas. Through experience and research, it has become evident that, for bone grafting to be successful, it must be given an isolated space to grow, protected from muscular pressure, tissue impingement and chewing forces. In order to create this space, many approaches have been proposed. For example, both Syers (U.S. Pat. No. 5,297,563) and Magnusson et al (U.S. Pat. No. 4,961,707) teach the use of a fabric-like membrane which is used over a bony defect. Although this barrier creates an isolated space from the invasion of epithelial cells into the bony defect or bone graft area, it does not create a protected space from chewing forces or tissue pressure.
Morgan (U.S. Pat. No. 5,380,328) teaches the use of a composite perforated titanium mesh layered with polytetrafluoraethylene (PTFE or Teflon.RTM.) fibers. Even though this approach would be feasible for creating a protected space in order to grow bone, it has some severe limitations. This material requires the placement of peripheral bone screws into the edges of the meshed piece in order to create a direct fixation of the titanitum mesh to the jaw bone and then bowing-up or tenting-up the center area in order to create the protected space. Often, it would not be feasible to place the peripheral bone screws in the peripheral areas for fear of damage to the inferior alveolar nerves or sinus penetration or damage to nearby tooth roots. The protrusion of these screws above the mesh is also of concern as potentially causing a tissue irritation complication with this given procedure.
Furthermore, the difficulty of forming the exact amount of tenting desired with this material is inherently very difficult to control. Additionally, the removal of this material is complicated by the need to surgically dissect much deeper to locate the peripheral screws. This technique would also be expensive and time consuming to emplace due to the need for multiple screws to secure a single mesh
On the other hand, as will become more apparent below, the guided-tissue regeneration plate support and fixation system contemplated in accordance with the subject invention obtains the ability to place a single screw in the center of the bone graft area, thereby facilitating the selection of a screw height that allows for an exact amount of tenting, thus giving the support where it is needed most. Placement and removal of this device is greatly simplified due to the fact that peripheral screws are not required (although such can be used). The head of the screw ends up being mostly under the plate, thus preventing any concern about screw-head irritation or prousion. Furthermore, concern about danage to neighboring peripheral structures is eliminated. In general, a much more simplified and cost effective method, apparatus and result are achieved.
Experience with and further development of the guided-tissue regeneration plate support and fixation system has resulted in an important advance which enhances its effectiveness in practice. It has been found that the use of a fine mesh screen spanning open areas of a guided-tissue regeneration support plate results in a faster and more complete bone regeneration of the underlying bony ridge and faster and more healthy growth of the overlying periosteum. The fine mesh screen can be fabricated from any suitable material, resorptive or non-resorptive, and an especially suitable material especially when a titanium guided-tissue support plate is employed, is fine mesh screen titanium fixed to the support plate by welding, particularly spot or laser welding, by an adhesive or by sintering the two-piece assembly. Alternatively, a functional equivalent to a fine mesh screen region can be obtained by substantially reducing the thickness of predetermined central areas of an imperforate titanium (for example) plate and then perforating the reduced thickness regions with finely spaced apertures.